Why was the time around 600bce called the dark age?

It was called the dark age because back then people forgot how to read and write and the type of leader who became to power in grease was in 600 bc 

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.